Which type of module connects to sensors that measure process conditions in a modular PLC?

• A. Input module
• B. Output module
• C. Power module
• D. Communication module

Answer: (A)

Sensors that monitor process conditions feed into the PLC through an input module. This module acts as the interface to the field devices, handling signals from sensors (whether analog like 4–20 mA or 0–10 V, or digital on/off) and conditioning or isolating them so the PLC can safely read, interpret, and process the data. The input module converts those sensor signals into a digital form the controller can use for decision-making. The other module types serve different roles—an output module drives actuators, a power module supplies the system, and a communication module links the PLC to other devices—so the input module is the direct connection point for sensors measuring process conditions.